/* eslint-env amd */
define([],
function() {
	/**
	 * @fileoverview Object to handle access and retrieval of tokens.
	 * @author Brandon Mills
	 * @copyright 2014 Nicholas C. Zakas. All rights reserved.
	 * @copyright 2014 Brandon Mills. All rights reserved.
	 */
	//------------------------------------------------------------------------------
	// Implementation
	//------------------------------------------------------------------------------

	return function(tokens) {
		var api = {},
			starts = Object.create(null),
			ends = Object.create(null),
			index, length, range;

		/**
		 * Gets tokens in a given interval.
		 * @param {int} start Inclusive index of the first token. 0 if negative.
		 * @param {int} end Exclusive index of the last token.
		 * @returns {Token[]} Tokens in the interval.
		 */
		function get(start, end) {
			var result = [],
				i;

			for (i = Math.max(0, start); i < end && i < length; i++) {
				result.push(tokens[i]);
			}

			return result;
		}

		/**
		 * Gets the index in the tokens array of the last token belonging to a node.
		 * Usually a node ends exactly at a token, but due to ASI, sometimes a
		 * node's range extends beyond its last token.
		 * @param {ASTNode} node The node for which to find the last token's index.
		 * @returns {int} Index in the tokens array of the node's last token.
		 */
		function lastTokenIndex(node) {
			var end = node.range[1],
				cursor = ends[end];

			// If the node extends beyond its last token, get the token before the
			// next token
			if (typeof cursor === "undefined") {
				cursor = starts[end] - 1;
			}

			// If there isn't a next token, the desired token is the last one in the
			// array
			if (isNaN(cursor)) {
				cursor = length - 1;
			}

			return cursor;
		}

		// Map tokens' start and end range to the index in the tokens array
		for (index = 0, length = tokens.length; index < length; index++) {
			range = tokens[index].range;
			starts[range[0]] = index;
			ends[range[1]] = index;
		}

		/**
		 * Gets a number of tokens that precede a given node or token in the token
		 * stream.
		 * @param {(ASTNode|Token)} node The AST node or token.
		 * @param {int} [beforeCount=0] The number of tokens before the node or
		 *     token to retrieve.
		 * @returns {Token[]} Array of objects representing tokens.
		 */
		api.getTokensBefore = function(node, beforeCount) {
			var first = starts[node.range[0]];
			return get(first - (beforeCount || 0), first);
		};

		/**
		 * Gets the token that precedes a given node or token in the token stream.
		 * @param {(ASTNode|Token)} node The AST node or token.
		 * @param {int} [skip=0] A number of tokens to skip before the given node or
		 *     token.
		 * @returns {Token} An object representing the token.
		 */
		api.getTokenBefore = function(node, skip) {
			return tokens[starts[node.range[0]] - (skip || 0) - 1];
		};

		/**
		 * Gets a number of tokens that follow a given node or token in the token
		 * stream.
		 * @param {(ASTNode|Token)} node The AST node or token.
		 * @param {int} [afterCount=0] The number of tokens after the node or token
		 *     to retrieve.
		 * @returns {Token[]} Array of objects representing tokens.
		 */
		api.getTokensAfter = function(node, afterCount) {
			var start = lastTokenIndex(node) + 1;
			return get(start, start + (afterCount || 0));
		};

		/**
		 * Gets the token that follows a given node or token in the token stream.
		 * @param {(ASTNode|Token)} node The AST node or token.
		 * @param {int} [skip=0] A number of tokens to skip after the given node or
		 *     token.
		 * @returns {Token} An object representing the token.
		 */
		api.getTokenAfter = function(node, skip) {
			return tokens[lastTokenIndex(node) + (skip || 0) + 1];
		};

		/**
		 * Gets all tokens that are related to the given node.
		 * @param {ASTNode} node The AST node.
		 * @param {int} [beforeCount=0] The number of tokens before the node to retrieve.
		 * @param {int} [afterCount=0] The number of tokens after the node to retrieve.
		 * @returns {Token[]} Array of objects representing tokens.
		 */
		api.getTokens = function(node, beforeCount, afterCount) {
			return get(
				starts[node.range[0]] - (beforeCount || 0),
				lastTokenIndex(node) + (afterCount || 0) + 1
			);
		};

		/**
		 * Gets the first `count` tokens of the given node's token stream.
		 * @param {ASTNode} node The AST node.
		 * @param {int} [count=0] The number of tokens of the node to retrieve.
		 * @returns {Token[]} Array of objects representing tokens.
		 */
		api.getFirstTokens = function(node, count) {
			var first = starts[node.range[0]];
			return get(
				first,
				Math.min(lastTokenIndex(node) + 1, first + (count || 0))
			);
		};

		/**
		 * Gets the first token of the given node's token stream.
		 * @param {ASTNode} node The AST node.
		 * @param {int} [skip=0] A number of tokens to skip.
		 * @returns {Token} An object representing the token.
		 */
		api.getFirstToken = function(node, skip) {
			return tokens[starts[node.range[0]] + (skip || 0)];
		};

		/**
		 * Gets the last `count` tokens of the given node.
		 * @param {ASTNode} node The AST node.
		 * @param {int} [count=0] The number of tokens of the node to retrieve.
		 * @returns {Token[]} Array of objects representing tokens.
		 */
		api.getLastTokens = function(node, count) {
			var last = lastTokenIndex(node) + 1;
			return get(Math.max(starts[node.range[0]], last - (count || 0)), last);
		};

		/**
		 * Gets the last token of the given node's token stream.
		 * @param {ASTNode} node The AST node.
		 * @param {int} [skip=0] A number of tokens to skip.
		 * @returns {Token} An object representing the token.
		 */
		api.getLastToken = function(node, skip) {
			return tokens[lastTokenIndex(node) - (skip || 0)];
		};

		/**
		 * Gets all of the tokens between two non-overlapping nodes.
		 * @param {ASTNode} left Node before the desired token range.
		 * @param {ASTNode} right Node after the desired token range.
		 * @param {int} [padding=0] Number of extra tokens on either side of center.
		 * @returns {Token[]} Tokens between left and right plus padding.
		 */
		api.getTokensBetween = function(left, right, padding) {
			var currentPadding = padding || 0;
			return get(
				lastTokenIndex(left) + 1 - currentPadding,
				starts[right.range[0]] + currentPadding
			);
		};

		/**
		 * Gets the token starting at the specified index.
		 * @param {int} startIndex Index of the start of the token's range.
		 * @returns {Token} The token starting at index, or null if no such token.
		 */
		api.getTokenByRangeStart = function(startIndex) {
			return tokens[starts[startIndex]] || null;
		};

		return api;
	};
});